A laminated piezoelectric element is a driving element that is very effective for high-precision positioning. The laminated piezoelectric element comprises many layers of piezoelectric material such as PbZrO3—PbTiO3 (PZT), which has excellent high-speed responsiveness and can produce a great force. However, the displacement of this piezoelectric element for drive is very small (about 1/1,000 of the laminate height). Further, there is a problem that if a substantial shear load is applied to the piezoelectric element itself, the bonding surfaces on which the layers of piezoelectric material and electrodes are alternately connected easily break. Thus, it is necessary to take account of methods of fixing and supporting the piezoelectric element, connection with parts to be driven, etc. If the single piezoelectric element is to be used as an actuator, therefore, it is very awkward to handle and requires certain countermeasures.
Accordingly, an actuator is proposed in which a laminated piezoelectric element is combined with a displacement magnification mechanism that geometrically enlarges a small displacement produced by the piezoelectric element and, at the same time, facilitates attachment to fixing portions and parts to be driven. Another actuator is proposed in which a laminated piezoelectric element is combined with a translation mechanism that directly converts a great thrust or small displacement produced by the piezoelectric element into a rectilinear motion without magnification, and at the same time, facilitates attachment to fixing portions and parts to be driven, based on a high resonance characteristic inherent to the piezoelectric element. Still another actuator is proposed in which a restraint plate is affixed to a movable part of a displacement magnification mechanism with a viscoelastic body therebetween, in order to suppress a high resonance amplitude that affects the control performance, incidentally making use of a high resonance characteristic of a piezoelectric element, thereby reducing a large amplitude of a resonance peak of the movable part.
However, if the damping mechanism comprising the viscoelastic body and restraint plate is applied to the actuator that comprises the translation mechanism configured to convert a thrust of the laminated piezoelectric element into a rectilinear motion, not the displacement magnification mechanism comprising a parallel link and lever mechanism, a sufficient damping effect cannot be achieved although the viscoelastic body is strained due to extension by the same laminated piezoelectric element. Thus, it can be assumed that, in the translation mechanism configured to directly transmit a thrust or displacement of the piezoelectric element, the viscoelastic body cannot be effectively strained by the combination of the viscoelastic body and restraint plate, so that the vibration damping effect is reduced.
This invention has been made in view of these circumstances, and its object is to provide a damping method and an actuator with a damping mechanism, configured so that the inherent resonance peak of the actuator can be sufficiently damped without degrading the characteristics of the actuator that comprises a piezoelectric element and a translation mechanism.